1. Field of the Invention
The invention relates to a device that reduces torsional vibration by a reciprocating motion or a pendulum motion of an inertial mass body.
2. Description of Related Art
Japanese Patent Application Publication Nos. 2012-145190 and 2013-185653 disclose a torsional vibration reducing device configured to reduce torsional vibration by pressing a mass body having a disk shape or a cylindrical shape with a short axial length against a rolling surface of a rotating body that receives the torsional vibration by a centrifugal force, and reciprocating the mass body in a circumferential direction along the rolling surface when torque fluctuates. The rolling surface in the device described in JP 2012-145190 A and JP 2013-185653 A is formed in an inner wall portion on an outer side in a radial direction of the rotating body out of inner wall portions of each of accommodating chambers formed so as to be arranged at predetermined intervals in the circumferential direction of the rotating body. In a device described in Japanese Patent Application Publication No. 2014-47805, a rolling surface is composed of a first rolling guide surface and a second rolling guide surface having different arc shapes from each other. The first and second rolling guide surfaces are continuous in a circumferential direction, and are alternately formed.
In a device in which a rolling body is disposed in an accommodating chamber, and vibration is reduced by a reciprocating motion of the rolling body, the rolling body is configured to be freely movable within the accommodating chamber. Therefore, when a rotating body rotates, the rolling body is pressed against a rolling surface by a centrifugal force. When acceleration in a rotating direction is generated by fluctuations in torque of the rotating body in the above state, the rolling body moves along the rolling surface. An operating state as described above is generated when a rotation speed of the rotating body is relatively high, and the centrifugal force applied to the rolling body is thus large enough to press the rolling body against the rolling surface. In other words, when the centrifugal force is not sufficiently large, the rolling body falls to a lowest portion in each accommodating chamber by gravity. When the rotating body is stopped, the rolling body remains in the lowest portion in the accommodating chamber. On the other hand, in a case in which the rotating body rotates at a rotation speed at which a sufficient centrifugal force is not applied to the rolling body, an orientation in a vertical direction of the accommodating chamber is reversed when the accommodating chamber starts to descend after reaching a top portion in the rotating direction. Thus, the rolling body in the accommodating chamber falls to a lowest portion in the accommodating chamber. In the device described in JP 2012-145190 A and JP 2013-185653 A, in a case in which the plurality of accommodating chambers are independent of each other, and a partition wall portion is provided between the respective accommodating chambers, the rolling body may generate noise or abnormal sound by colliding with the partition wall portion when the rolling body falls as described above. In the device described in JP 2014-47805 A, since the rolling surface is continuous over an entire periphery of the rotating body, a connection member is provided so as to separate the rolling bodies, so that collision of the rolling bodies with each other, and generation of abnormal sound resulting from the collision are prevented. That is, in a configuration described in JP 2014-47805 A, since a portion corresponding to the partition wall portion with which the rolling body collides does not exist, the falling of the rolling body by gravity when the rotation speed is low, and the generation of the abnormal sound resulting from the falling do not possibly occur.